In service station environments, fuel is delivered to fuel dispensers from underground storage tanks (UST), sometimes referred to as fuel storage tanks. USTs are large containers located beneath the ground that contain fuel. A separate UST is provided for each fuel type, such as low octane gasoline, high octane gasoline, and diesel fuel. In order to deliver the fuel from the USTs to the fuel dispensers, a submersible turbine pump (STP) is provided that pumps the fuel out of the UST and delivers the fuel through a main fuel piping conduit that runs beneath the ground in the service station.
Due to regulatory requirements governing service stations, the main fuel piping conduit is usually required to be double-walled piping. Double-walled piping contains an inner space that carries the fuel. An outer annular space, also called an “interstitial space,” surrounds the inner space so as to capture and contain any leaks that occur in the inner space, so that such leaks do not reach the ground. An example of double-walled fuel pipe is disclosed in U.S. Pat. No. 5,527,130, incorporated herein by reference in its entirety.
It is possible that the outer annular space of the double-walled fuel piping could fail, thereby leaking fuel outside of the fuel piping if the inner space were to fail as well. Fuel sump sensors that detect leaks are located underneath the ground in the STP sump and the fuel dispenser sumps. These sensors detect any leaks that occur in the fuel piping at the location of the sensors. However, if a leak occurs in the double-walled fuel piping between these sensors, it is possible that a leak in the double-walled fuel piping will go undetected since the leaked fuel will leak into the ground, never reaching one of the fuel leak sensors. The STP will continue to operate as normal, drawing fuel from the UST; however, the fuel may leak to the ground instead of being delivered to the fuel dispensers.
Therefore, there exists a need to be able to monitor the double-walled fuel piping to determine if there is a leak or breach in the outer wall. Detection of a leak or breach in the outer wall of the double-walled fuel piping can be used to generate an alarm or other measure so that preventive measures can be taken to correct the leak or breach in the outer wall of the double-walled piping before a leak in the inner piping can escape to the ground.
Recent proposed changes in state and federal regulations will tighten the requirements to contain leaks and will further require better leak detection so that environmental damage may be minimized. As a result, it is becoming imperative that all potential leak sources be evaluated and steps taken to detect and contain leaks in the piping systems. One area that has not been specifically addressed by the parent disclosures is within the submersible turbine pump and in the riser pipe that connects the submersible turbine pump to the UST.